An electrostatographic printer is known in which a toner image in powder form is deposited on a moving transfer member and a substrate is fed along a substrate path into contact with the transfer member, whereby the toner image is transferred to one face of the substrate. To improve the quality of image transfer to the substrate, it has been proposed to heat the toner image on the transfer member in advance of the transfer of the toner image to the substrate and to cool the transfer member following the transfer of the toner image therefrom to the substrate to a temperature below the glass transition temperature T.sub.g of the toner, prior to the deposition of further toner images on the transfer member. At the transfer site, a pressure roller is positioned in opposition to the transfer member to form a transfer nip therebetween, through which the substrate path passes.
While such a construction is able to produce good quality results, it is found that the quality of transfer to the substrate is not consistent, there being a variation between the quality when the printer is started up after an idle period and the quality after the printer has been running for some time.